Terrestrial Isopods Generate Microplastics from Low‐Density Polyethylene Without Effects on Survival

Abstract

With concern growing regarding the impact of microplastics (MPs) on terrestrial ecosystems, it is important to assess the role invertebrates may play in the fate of MPs within these ecosystems. MPs commonly enter these environments through improperly discarded waste or the application of treated biosolids and/or wastewater on agricultural soils. This study investigated whether three species of terrestrial isopod (Porcellio scaber, Porcellio laevis, and Porcellionides pruinosus) ingest plastic debris and generate MPs during exposures varying from 24‐h up to 14 days and whether this may have an adverse effect on their health. Test vessels were designed to expose isopods to plastic fragments in the form of polyethylene plastic foam. Isopods were exposed to plastic that was either a) pristine, or b) weathered in a soil and water solution prior to incorporation in test vessels. When exposed to weathered polyethylene, all three species generated MPs (min‐max size values for all durations inclusive: P. laevis = 114 – 1673 µm; P. scaber = 99 – 1635 µm; P. pruinosus = 85 – 1113 µm) through the consumption of macroplastic fragments with no observed impact on their health. In the shorter duration exposures, the number of MPs generated by the isopod species in this study was highly variable between experimental vessels (min‐max generated MPs for 14‐day exposure: P. laevis = 25 ‐ 420; P. scaber = 50 – 583; P. pruinosus = 48 ‐ 311). However, as the exposure durations increase there was a clear trend of increasing MP generation, indicating that the isopods continued to consume the plastic fragments so long as the surface was weathered. A significant difference in the size of generated MPs was observed as well, with smaller isopod species generating smaller MP fragments on average. The results of this study confirm that certain species of isopod can contribute to the generation of MPs, which constitutes an additional pathway of MPs exposure to soil ecosystems.